Reactor Having a Sacrificial Anode

ABSTRACT

A reactor is proposed that comprises a cathode and a sacrificial anode, in which a spacing between cathode and anode is kept constant by the cathode following, or tracking, the anode.

Reactors that have a cathode and an anode are often used in processtechnology. In the operation of the reactor, an electrical voltage isapplied between the cathode and anode such that the anode is consumed(sacrificial anode).

DE 10 2010 050 691 B3 and DE 10 2010 050 692 B3 describe a method and areactor for recovery of phosphate salts from a liquid, where thesacrificial electrodes consist of a magnesium-containing material. Theinvention is based on the task of making available a reactor thatcomprises a cathode and an anode (sacrificial anode) that ensures betterprocess conduct and consequently better results with minimizedelectricity consumption and optimum utilization of the material of thesacrificial anode at the same time. In addition, the operating costshould be minimized.

This task is solved according to the invention by a reactor comprising ahousing, a cathode, and an anode, where the cathode and the anodedelimit a channel and where the cathode can be moved in the housingrelative to the anode.

In this way, a distance between the cathode and anode is always constantindependent of the consumption of the anode. Consequently, theelectrical field between the anode and cathode is always the same andoptimum conversion rates are achieved in the reactor with low energyconsumption at the same time.

As a rule, it is advantageous if the cathode, which is not consumed, ismoved relative to the anode. As a rule, the cathode is made of stainlesssteel or another corrosion-resistant electrically conductive material.Therefore, it is advantageous to accommodate the cathode such that itcan slide in the reactor housing. The desired relative movement betweenthe cathode and the stationary anode arranged in the housing can bebrought about in this way. It is of particular importance in conductingthe process that the spacing S between the surfaces of the anode andcathode remains constant regardless of the consumption of the anode.These surfaces delimit a channel through which the liquid being treatedflows. Thus, if the geometry of the channel and the electrical fieldthat is present between the electrodes (anode and cathode) are constant,specific and very good conversion rates are achieved with minimal energyconsumption.

In an advantageous embodiment of the invention, the desired constantspacing S can be achieved by at least one electrically nonconductivespacer, for example one made of plastic, being disposed between thesurfaces of the anode and cathode delimiting the channel. As a rule, itis advantageous to provide at least two spacers in order to preventtilting of the anode and cathode. These spacers are dimensioned so thatthe spacing S is maintained regardless of the consumption of the anode.

The spacing S can also be kept constant by means of gravity, one or moresprings, and/or one or more actuators. If gravity is utilized, forexample, to track the cathode to the anode, then arranging the anodebelow the cathode in the vertical direction is a possibility, so thatthe cathode is moved in the direction of the anode by the force ofgravity. If at least one spacer according to the invention is disposedbetween the surfaces of the anode and cathode that delimit the channel,then the spacing between the surfaces of the anode and cathode thatdelimit the channel are always kept constant in a very simple andreliable way, independent of the consumption of the anode.

Of course, it is also possible in principle to arrange the anode abovethe cathode and to move the anode in the direction of the cathode bymeans of gravity. Instead of or in support of gravity, the anode or thecathode can be moved with the help of springs, or with the help ofactuators, or electrically, pneumatically, or hydraulically, in order tocompensate the material loss of the sacrificial anode and to maintain aconstant spacing S between the surfaces of the anode and cathode thatdelimit the channel.

If actuators are used for tracking the cathode, regulation or control ofthe spacing between anode and cathode can be provided with sensors,which, as a part of the control circuit, register the consumption or theremaining thickness of the anode. Any suitable sensor types that areavailable on the market could be used.

The spacing S between the surfaces delimiting the channel can be keptconstant most easily if the surfaces of the anode and cathode delimitingthe channel are planar. It is further particularly advantageous if thesurfaces of the cathode and/or anode delimiting the channel arerectangular. Since an unconsumed anode has a certain thickness, theanode has a cubical shape.

In particular, it is advantageous if the outer dimensions (length andwidth) of the housing of the reactor according to the inventioncorrespond with the dimensions of current transport systems, for examplethe so-called Euro pallets. Then the lower part, specifically, of thehousing can be employed as a reusable transport container for the anodesand can be transported in the existing supply chains at optimal cost.For instance, a plurality of lower parts with anodes can be stacked ontop of each other and bound into a stack, which is then transported toor instead of a Euro pallet and brought to the reactor. In doing so, thetransport capacity of a truck or freight train can be utilized in thebest possible way, so that transport costs are minimized. In addition,it is possible to move the stacked lower parts, which are loaded withthe anodes according to the invention, for example, with a forklift or apallet truck on site, i.e., in a treatment plant, and to insert theminto the reactor. In another advantageous embodiment of the invention,it is provided that the surfaces of the cathode delimiting the channelhave a plurality of openings, which act as flushing nozzles. The channelcan be cleaned and flushed with a liquid through these nozzles, so thatdeposits and encrustations that are deposited in the channel during theoperation of the reactor can be flushed away.

It is possible to make said opening in the cathode because the cathodeis not subject to any wear. However, it is also possible to make theseopenings in the anode. It is provided in another advantageous embodimentof the invention that the cathode have a distribution chamber, and thatthe openings are hydraulically linked to the distribution chamber. Thenit is possible to simply pump the cleaning liquid under sufficientlyhigh pressure into the distribution chamber. From there, the cleaningfluid passes through the openings into the channel and flushes away anydeposits that may be on the surfaces delimiting the channel. Thecleaning of the walls delimiting the channel by means of the flushingopenings can take place continuously, at fixed intervals, or independence on an indicator. Such an indicator, which triggers thecleaning, can be, for example, the current and/or the voltage betweenthe electrodes, or parameters derived from these signals.

To be able to register the process occurring in the reactor and theconsumption of the sacrificial anode, means for registering the positionof the cathode and/or the anode are provided in the reactor according tothe invention. Said means for registering the position of the anodeand/or the cathode can be, for example, a position sensor of any design.Said position sensor is advantageously affixed to the electrode that isdisposed so that it can move in the reactor housing. In this way, thedegree of consumption of the sacrificial anode can be monitored simplyand very reliably.

Finally, means are provided for registration of the electrical currentthat flows between the anode and cathode, and/or the electrical voltagethat is applied between the anode and cathode. In this way, the processtaking place in the reactor can be monitored simply and reliably.Possible disruptions of the process lead to changes of the electricalcurrent and/or the electrical voltage and thus can easily be detected.

The anode preferably consists of a magnesium-containing material. It canalso be more or less pure magnesium. As a rule, the cathode is made ofstainless steel, since this material is electrically conductive and willnot be attacked by the liquid that is treated in the reactor.

Other advantages and advantageous embodiments of the invention arepresented in the following figures.

DRAWINGS

Here:

FIG. 1 shows a lengthwise section through an embodiment example of areactor according to the invention.

FIGS. 2A, 2B and 2C show three different states of the sacrificialanode.

FIG. 3 shows a plurality of reactors connected in series and inparallel.

DESCRIPTION OF THE EMBODIMENT EXAMPLE

In this embodiment example, the reactor according to the inventionconsists of a two-part housing with a lower part 1 and an upper part 4.The housing can be separated along a horizontal separation plane inFIG. 1. The contact surface between the lower part 1 and the upper part4 is indicated with the reference number 21. The separation plane alsolies there.

A circumferential seal 23, which can be made, for example, as an O-ring,is disposed in the region of the contact surface 21 so that the liquidinside the housing does not get into the environment.

In order to be able to seal the upper part 4 tightly to the lower part 1of the reactor, there are additionally closures 8 arranged in the regionof the contact surface. By opening the closures 8, the upper part 4 canbe separated from the lower part very quickly and with low personnelcost.

In this embodiment example, the lower part 1 accommodates a sacrificialanode 2, which consists of a magnesium-containing material, if thereactor is used, for example, for recovery of phosphate salts from aliquid. One such process is described in the applicant's DE 10 2010 050691 B3. Using the reactor according to the invention, it is possible, byapplying a low electrical DC voltage, to supply magnesium ions to thephosphate- and ammonium-containing liquid and to split the watercontained in the liquid into OH⁻ and H⁺ ions, so that the pH becomeselevated and the reactions needed for precipitation can take place.Through the low energy demand and the omission of the feed of an alkalito raise the pH value, the costs for operating the system are lower thanin the process known from the prior art. A pH of about 9 is desirablefor the desired precipitation.

Since hydrogen builds up in the operation of the reactor, in the upperpart 4, there is a connection 28 through which the hydrogen can be drawnoff and sent to another use.

Of course, the anode 2 can also consist of a different material if theprocess in the reactor according to the invention requires it.

The anode 2 is made as a rectangular plate having a certain thickness;therefore, it is, if all three dimensions are considered, cubical.Frequently, the anode 2 consists of a magnesium-containing material,which must be transported safely and without damage.

This is why provision is made according to the invention to use thelower part 1 at the same time as a reusable transport container for theanode 2. In order to optimize the transport of the lower parts 1, thelower parts 1 preferably have the dimensions of a Euro pallet or anotherstandardized transport container. It is especially preferable if theempty lower parts 1 can be nested. In this way, the transport of theanode 2 from the manufacturer of anode 2 to the user and of the emptylower parts from the user to the manufacturer becomes optimized.

A cathode 3, which as a rule is made of stainless steel, is disposedabove the anode 2. The cathode 3 is accommodated in the upper part 4 ofthe housing so as to be guided in it, such that the cathode 3 moves inthe direction of the anode 2 under the effect of gravity.

To keep the cathode 3 from lying directly on the anode 2, spacers 9 arearranged between the anode 2 and the cathode 3. The distance between thesurface 25 of the anode 2 and the surface 27 of the cathode 3, whichdelimit a channel 10, is called the spacing S. A liquid that is beingtreated in the reactor flows through the channel 10. The spacing S is animportant parameter for optimizing the functioning and/or the energyconsumption of the reactor. This is why it is very advantageous that thespacing S can be established simply and precisely in correspondence withthe requirements of the specific case by means of the spacers 9.

The lateral boundaries (side walls) of channel 10 are not visible in thelengthwise section in FIG. 1. The side walls of the channel 10, which isrectangular in cross section, are formed by the lower part 1 and theupper part 4 of the housing.

In this embodiment example, the surfaces 25 and 27 delimiting thechannel 10 are planar. Thus it is extremely simple to keep the spacing Sbetween anode 2 and cathode 3 constant, independent of the consumptionof the anode 2.

The upper part of the housing 4 has an inlet 5 and an outlet 6. Theliquid to be treated in the reactor is supplied via the inlet 5 and thenflows through the channel 10, which is rectangular in cross section,between the anode 2 and the cathode 3 to the outlet 6. The transitionregions 31 between the inlet 5 and the channel 10 and between thechannel 10 and the outlet 6 are dimensioned very generously.

Of course, it is also possible to provide the inlet 5 and the outlet 6in the lower part of the housing 1 [sic; lower part 1 of the housing].Combinations are also possible. If the lower parts 1 are used astransport containers, it is advantageous if there are no connections inthe lower part 1, since this simplifies the exchange of lower parts 1and the anodes 2 in them.

In the operation of the reactor, deposits can form on the surfaces 25and 27 of channel 10, which will impede the liquid treatment process oreven make it impossible. To be able to remove such deposits during theoperation of the reactor, a distribution chamber 11 and a plurality offlushing nozzles 12 are made in the cathode 3. The distribution chamber11 is supplied with a cleaning liquid as necessary via a connection,which is not shown. The cleaning liquid is pumped into the distributionchamber 11 at sufficient pressure and in a sufficient amount and flowsthrough the flushing nozzles 12 into channel 10. Through the number offlushing nozzles 12 and their arrangement and design, in combinationwith the pressure of the flushing liquid in the distribution chamber 11,it is possible to remove even stubborn deposits on the surface 25 ofanode 2, as well as on surface 27 of cathode 3.

The liquid that is to be treated in the reactor can be used as theflushing liquid. In this case, the flushing effect is ultimatelyachieved through the kinetic energy with which the flushing liquid flowsthrough the flushing nozzles 12 and strikes surface 25. Through thedeflection of the flushing liquid at surface 25, the flushing liquidalso reaches surface 27 and cleans it.

However, it is also possible to use a flushing liquid containingcleaning additives or chemically active substances.

The anode 2 is electrically contacted, for example, via an electricalcontact 14. Correspondingly, cathode 3 is contacted via an electricalcontact 15. The electrical connections and the voltage source thatsupplies the anode 2 and cathode 3 with electric power are not shown inFIG. 1.

As already noted, cathode 3 can drop downward under the force ofgravity. This means that with increasing consumption of the anode 2, thecathode 3 will continue to fall farther downward in the direction of thelower housing part 1.

The invention makes use of this effect in that the position of thecathode 3 relative to the upper part 4 of the housing is used as anindicator for the consumption of anode 2. This relationship is explainedin more detail by means of FIGS. 2A, 2B and 2C. In each case, means forregistering the position of the cathode (also called position sensor 7below) are arranged on the upper part 4 of the housing. Said positionsensor can be a commercially available position sensor.

The relationship between the consumption of the sacrificial anode 2 andthe position of the cathode 3 relative to the upper part 4 of thehousing is illustrated in three stages in FIGS. 2A-2C.

In FIG. 2A, the situation is presented as in FIG. 1. The sacrificialanode 2 is unused. Consequently, the cathode 3 has taken its highestpoint in the upper part 4 of the housing. Now, when the thickness of thesacrificial anode 2 decreases due to the continuous operation of thereactor, cathode 3 sinks farther downward and consequently a pin 29 ofthe position sensor 7 moves downward relative to the upper part 4 of thehousing. This situation is shown in FIG. 2B. At this point, thesacrificial anode 2 still has only about half the thickness of theunused state. The position of cathode 3 can be measured from therelative movement of the pin 29 relative to the upper part 4 of thehousing and, due to the spacer 9, the thickness of the sacrificial anode2 can also be determined.

In FIG. 2B, it can easily be seen that the channel 10, which isdelimited by the surfaces 25 and 27, likewise moves downward withincreasing consumption of anode 2. Consequently, transition regions 31made in the lower part 1 of the housing both at the inlet 5 and at theoutlet 6 must be sufficiently long, mainly in the vertical direction.This ensures that the treated liquid gets into channel 10 and from therereaches outlet 6 independent of the thickness of anode 2.

FIG. 2C shows the state in which the anode 2 has been completelyconsumed. In this state, the spacers 9 lie directly on the lower part 1of housing 1 [sic]. Of course, current can no longer flow through thecathode 3. Thus, the complete consumption of anode 2 can also bedetected through this decrease of the current to zero. Of course, it isalso possible to detect the complete consumption of anode 2 by detectingthe position of the output signal of the position sensor 7.

According to the invention, it is possible to operate a plurality ofreactors according to the invention in series and/or in parallel. Thisarrangement is shown schematically in FIG. 3.

It is possible here that, in each case according to the consumption ofanode 2, not all of the reactors will be supplied with electric voltage.Rather, there is the possibility of providing only a part of thereactors with electric power in correspondence with the amount ofaccruing liquid that must be treated.

When a plurality of parallel lines of reactors are present, it is alsopossible to hydraulically uncouple a reactor or a line of reactors fromthe system and then to replace at least one anode in the reactor or idleline. The operation, or the treatment of the liquid, can then becontinued in the parallel connected reactors or lines of reactorswithout interruption.

In FIG. 3, the reference numbers mean:

119 Inlet

120 Outlet

121 Sensor for measurement of phosphate content in outflow

122 Control

123 Power supply of a reactor

124 Output signal of position sensor 7

125 Output signal of sensor 121

126 Control signal of control 122 for the performance (voltage U and/orcurrent I) of a power supply 123

127 Output performance of a power supply 123

It becomes clear from this presentation that the performance of theoverall system is scalable in a very wide range by connecting anddisconnecting individual reactors or lines and, because of theredundancy of the parallel and series connected reactors, the overallsystem can be operated very reliably.

1. A reactor comprising a housing (1, 4), a cathode (3), and an anode(2), wherein the cathode (3) and the anode (2) delimit a channel (10),the cathode (3) being movable in the housing (4) relative to the anode(2).
 2. A reactor as in claim 1, wherein the anode is a sacrificialanode and a spacing (S) is included between surfaces (25, 27) of theanode (2) and the cathode (3) delimiting the channel (10), independentof consumption of the anode (2).
 3. A reactor as in claim 1, wherein atleast one electrically nonconductive spacer (9) is disposed betweensurfaces (25, 27) of the anode (2) and the cathode (3) that delimit thechannel (10).
 4. A reactor as in claim 3, wherein the spacing (S) iskept constant with the help of gravity, one or more springs, or one ormore actuators.
 5. A reactor as in claim 2, wherein the surfaces (25,27) of the anode (2) and the cathode (3) that delimit the channel (10)are planar.
 6. A reactor as in claim 2, wherein at least one of theanode (2) and the cathode (3) is rectangular.
 7. A reactor as in claim1, wherein the housing includes an upper part and a lower part, andwherein the lower part (1) serves as a transport container for the anode(2).
 8. A reactor as in claim 7, wherein outer measurements (L, B) ofthe lower part correspond to the measurements of a standardizedtransport system.
 9. A reactor as in claim 1, wherein a surface (27) ofthe cathode (3) that delimits the channel (10) or a surface (25) of theanode (2) that delimits the channel (10) has a plurality of flushingnozzles (12).
 10. A reactor as in claim 9, wherein the cathode (3) has adistribution chamber (11), and the flushing nozzles (12) arehydraulically linked to the distribution chamber (11).
 11. A reactor asin claim 1, further including means (7) for detection of the position ofthe anode (2) and/or the cathode (3).
 12. A reactor as in claim 1,further including means for detection of electrical current (I) thatflows between the anode (2) and the cathode (3), or electrical voltage(U) that is applied between the anode (2) and the cathode (3).
 13. Areactor as in claim 1, wherein the anode (2) is a sacrificial anode andcomprises a magnesium-containing material.
 14. A reactor as in claim 1,wherein a liquid containing phosphate salts flows through the channel,and phosphate salts are removed at the anode.
 15. A reactor as in claim3, wherein the surfaces (25, 27) of the anode (2) and the cathode (3)that delimit the channel (10) are planar.
 16. A reactor as in claim 5,wherein at least one of the anode (2) and the cathode (3) isrectangular.
 17. A reactor as in claim 2, wherein a surface (27) of thecathode (3) that delimits the channel (10) or a surface (25) of theanode (2) that delimits the channel (10) has a plurality of flushingnozzles (12).
 18. A reactor as in claim 3, wherein a surface (27) of thecathode (3) that delimits the channel (10) or a surface (25) of theanode (2) that delimits the channel (10) has a plurality of flushingnozzles (12).
 19. A reactor as in claim 5, wherein a surface (27) of thecathode (3) that delimits the channel (10) or a surface (25) of theanode (2) that delimits the channel (10) has a plurality of flushingnozzles (12).
 20. A reactor as in claim 2, further including means fordetection of electrical current (I) that flows between the anode (2) andthe cathode (3), or electrical voltage (U) that is applied between theanode (2) and the cathode (3).